Pan liner



Patented May 19, 1953 to Bestpak Inc., Boston,

of Massachusetts No Drawing. Application June 7, 1950,

Serial No. 166,770 1 1 Claim. 7 ('01. 8-120) This invention comprises anew and improved liner for baking pans, the liner being constructed ofcellulose base material and having a contact surface formed in situ bythe chemical reaction of the cellulose material with a reactingchemical, thus providing a surface which is physically integral with butchemically difierent from the base material.

A liner for baking pans should be non-toxic,

inert, flexible, and capable of withstanding the elevated temperaturesto which it will be subjected during baking. It is highly desirable tomake the liner of inexpensive construction and of such material that itwill not become adhered either to the pan or to the baked product duringany part of the handling and processing.

A primary object of my invention is to produce a liner for bakingutensils which is sturdy enough to aid materially in the handling andpackaging of baked product when removed from the utensil, which willpart readily from the baking utensil and at any later date will alsopart freely from the baked product leaving it whole and uncontaminatedand the liner clean and essentially in its original condition ready forfurther use if desired.

A further object of the invention is to use as the base for the improvedliner a material comprised chiefly of cellulose in the form of papersince the use of cellulosic material is an accepted feature of the tradedue to its low cost and general mechanical characteristics plus thedisposabllity feature.

Another object of my invention is to modify the chemical structure ofthe liner in such a way as to provide a new chemical surface but stillto retain the mechanical characteristics and mechanical integrity of thepaper structure.

A still further object is so to treat the cellulosic base materialchemically that only the new chemical surface can contact the baking panor the baked product.

Another object is to make available a process of treatment whereby papercan be converted to the desired form either in the sheet or in thedimensions of the finished liner.

Ordinary paper cannot be used as a liner in baking yeast raised productsinasmuch as the products stick to the paper so that the paper cannot beremoved from the baked product without leaving a substantial amount ofthe product on the paper. All previous attempts to solve this problemhave been based on providing a heavy coating of wax or shortening on thesurface of the paper. This melts almost immediately upon entering theoven Mass., a corporation with the resultthat the coating either entersthe paper orthe product or both, a condition which is not satisfactoryeitherfrom the point of view of the productor the package. Thesecoatings of wax or shortening may serve over a narrow range of productscontaining-a high shortening content or in which the sugar is in balancewith the shortening (one in which the percentage of sugar is not greaterthan the percentage of shortening); They are not satisfactory where. theproduct has a low shortening content or where the sugar is overbalanced.Under such conditions the product sticks badly, leaving much of theproduct on the lining.

I have discovered that the way to achieve the desired results is not tocoat paper with a mechanical film but rather to insure that the reactivechemical contacting the cellulose forms an integral chemical union withthe ultimate cellulose molecules and therebyforms a new surfacethroughoutthe paper structure comprising a fundamentally differentchemical structure adapted to the desired use but forming a continuousand integral part with the cellulose of the undisturbed paper structureitself.

In order to achieve this it is necessary that the reactive chemical bereacted with thecellulose of the paper in situ. The finished liner maybe treated in this manner butI prefer to contact and react the cellulosein sheet form with the reactive. chemical before the liners are cut fromthe paper sheet. i

Obviously, only those reactive chemicals capable of reactinglwithcellulose under the imposed conditions come within the scope oi. myinvention. Care must be taken in selecting the conditions to avoidruining the paper. structure with by-products from the reaction and toavoid too severe extremes of temperature, concentrations. etc., duringthe reaction.

I have found, for instance, that if acetic anhydride is dissolved inglacial acetic acid in the proper concentration (about 3%) and allowedto react (at a temperature not over 40 C.) with paper of. the krait,sulfite, news or parchment type, or with alpha pulp, a clear transparentfilm of cellulose acetate, chemically .distinct from but physicallyintegral with the smooth paper or pulp surface and probably only a fewmolecules in thickness can be formed. When the paper or pulp is washedand dried it is ready for use as a pan liner material in accordance withmy invention.

Further, benzoic anhydrlde if dissolved in 819.-

cial acetic acid and reacted with the cellulose 01' the paper canproduce the same satisfactory new chemical paper surface to act as aliner while leaving the mechanical form of the paper intact. In thiscase the protective film will be of cellulose benzoate.

In other fashion stearyl chloride can also be reacted with pulp, forinstance, by the well knowmschotteusliaumen reaction t'oformnazyeryeffective-new paper surface of'cellulose stcarate. Likewise benzoylchloride can be utilized. In each case the sodium hydroxide presentprotects the cellulose from action of hydrochloriccacid, thereby servinga necessarily useful function until the by-products can be i wsshed out.

In all the above mentionedcases, I'havefound' that a concentration ofabout 13% of the reactive esterifying chemical is sumeientand not inexcess to treat the pulp or paper to produce. an integral esterified andotherwise undisturbed surface on the paper. I have further found that aparticularly effective surface is fomewby a-'-. type of tcompound whichwill 1 not only-react with thecellulose but willalsopartlallypolymerizexduring the reaction e; to formaapolymerscellulose:complex. Such a 1 compound is foundamongthe-steario: acid-heavy metalvsalt complexes: ofwhichwon'e isstearato chromic: chloride when thisxmaterial imabout 3%Aconcentrationin watemandealcohol is wused tm-treatepapera such aa 'kraft,..sulflte,-'1 news or parchment rtwill-reaotto formeijust theklnd: of 1 newcellulosereomplexisurface. adequate toxmeet -"all -the' objectsMathis-invention: :-;One..-way in 1r which: :I, canamrform athiareactionto provide. the

paper with a new smoothsurfaceas by thefollowdng procedure:

The chlorideisadissolved in a mixture of'alcohol =('l!lthe1' ethylor-isopropyllzandwater sozthat the :=flnal rproperations:are about: 91water, '6 9a. alconnhol'aan'rl f3%;v:.nlcidicl'ilozrideicomplex:-To-this is Ladded a"; smallzamount: ofasodiumxformatesandurea:"dissolved'.in:water at aiconcentration' of =siaboutf-5%i:sodiumuformate andi'l5%r..urea. ,=:An mamount:rapproximately; ,eqmvalent toj; .the :...acid chloride in weightisziaddedz :JIhezpaper then passed through sthIS- E snlutiong; .furtherpassed .througlx-:squeeze.irolls..andasthen to audrienuwhere 'isthemeactiorr isecompletedz'i .xThe drier main- :1 stained, sinuta2l5Fxandz-maybeaseries ofwsteam 4;; heated rolls oner-hotaircdrier.ilanfterdryingrthe 1 1' paper issready'zforinse.

r :On thesother hand it .iszalsoipossibleto spray the chloride complexsolution-.idirectlyp.ontmthe a: surface of :.:=.the.-.zpaperiwbefore.rrdrvinech thereby r. .aachieving thegsame. effective.chemical:;surfacing but: atrsomewhat. added-100st and: inconvenience.:L have: also afound .that :azconcentration of-.-less 2' .than aofzithis chloride is; ineffective for :my 1.: :nse' while aconcentration ofeover 3% is; likewise .1 ineffective. Idonot try toexplainthis phenomenon but rather limit myself to use of this materialin concentration between and 3% in the treating solution.

In addition I have found that by treating my 5 new cellulose compositionsurface with a 2% or up to a 5% water solution of polyvinylalcohol, ofmedium viscosity, and then drying the paper again that ,I can form asurfacej with improved grease resistant properties. This is in addition10 to the cellulose composition film and is quite important inmanufacturing liners such as mine since all products which would bebaked and packaged in these liners contain shortening that -.:-=tendsto: penetrate as a grease. The use of poly .vinyl alcohol provides abarrier so that the shortening does not stain the package and does notleave, the product, thus retaining the goodness of x .the product withinitself.

To put polyvinyl alcohol on my new cellulose go-composition surface Isimply pass the treated paper through a water solution of polyvinylalcohol in 2 to 5% concentration and then throu h zzipsqueeze rolls toremove excess material from the y; sheet... On drying the paper is readyto becut intov liners.

Ihave found also, surprisingly..-enough, that :I ,can add the; polyvinylalcohol ,directly. to my i'chloride solution in the process of making itand achieve good results by the simultaneous appligo-l'cation ofwthereacting chemical and the, coating chemical to the paper.

;.Having thus disclosed my, invention and described in detail several,embodiments thereof, I 1 q-claim as new anddesirev to secure by Lettersz-Patent:

. A- newand improvedpan liner-comprising a body of paper-havinga-smooth,-lundisturbedand integral surface portion thereof-which, hasbeen z converted in, situ-into an-esterified cellulose com- 40:,position selected from the group consisting: of zcelluloseacetate,,cellulose-benzoate and cellulose estearateu thesaidrsurface;portion being. .capable of withstanding, elevated; bakingtemperatures pwithoutdmpairing its; characteristic of. freely parting;from the baked product.

ccPAULs'IHOMPSON.

Referencesflited inthe -file of this, patent UNITED STATES-PATENTSNumber Name Date Q1,546,211 ,Dreyfus July 14, 1925 1,659,399 vFaber',Feb, 14, 1928 1,680,934 Buel Aug. 14-, 1928 1,840,404 Malm Jan. 12,1932 1,897,026 Karrer b, 7,1933 '1 2,218,388 Twombly Oct. 15, 19402,328,844 .Osterhof a- Sept. 7,1943 2,362,580 Nadeau et al. Nov. 14,1944 2,370,419 Ray Feb. 27, 1945

